While the word “refurbishment” is often applied to actions taken at any point during HWR service to return a SCC to its original functional capability, in this report “refurbishment” means those actions taken near end-of-design life, for HWR PLiM.

The key element for HWR PLiM is fuel channel replacement (FCR), as there are known degradation mechanisms that will limit the life of the pressure tubes. The overall approach is to perform both the FCR work as well as any other necessary refurbishment work. The FCR work is also an opportunity to refurbish other HWR systems or components to ensure that an extended service life will be achieved without the need for another extended outage.

During the planning period, assessments and plans are made to identify the detailed scope of those specific systems, components and structures for which the FCR outage provides the most economic opportunity to inspect and maintain or replace. It is important to clearly define the required work scope upfront in order to ensure that the FCR outage duration is not lengthened or burdened with the cost of maintenance work, which could otherwise be accomplished during future station outages.

PLiM planning establishes the timing of replacement of major pieces of equipment so that estimates can be made of the expenditures to be expected during the refurbishment project and subsequent operation. One process to identify what work is required consists of the following steps: [2] [3]

(3) Confirmation of SSC lists — The equipment database from the NPP is used as the basis for defining all the component parts that are addressed for each CA report. However, experience has also shown that these databases may not be sufficiently developed in all areas to be used as a reliable basis for the CA. Therefore, confirmation of the SCC list for each system may be required based on Design Manuals, Operating Flowsheets and other relevant information.

(4) Screening — The next step is to screen out from the CA process all items that are normally replaced in the plant as part of current maintenance programmes. Items were removed from further consideration if:

• The devices can be out of service for short periods of time without requiring plant shutdown

• Work order history revealed no problems resulting in unit outages

• Devices can be isolated for easy refurbishment/replacement

• Devices are readily accessible

• Replacement of devices does not require significant capital or maintenance costs

• Replacement of devices is possible on power or during a normal outage

• Replacements/spares are part of existing inventory or readily available

(5) SSC health prognosis — Items that are not screened out are subjected to a detailed assessment process consisting of the following items:

• Review of the SSC design basis

• Review of historical operational and maintenance data, primarily the work order history, supplemented by system engineer interview

• Identification of ageing related degradation mechanisms and evaluation of the SSC against each relevant mechanism.

• Identification of any known obsolescence issues

•Generation of conclusions about the health prognosis for the SSC and recommendations.

Any decisions made are retained in a database for later implementation. Using a systematic process such as the one described above should result in a highly effective and auditable process to scope the refurbishment work.